Multilayer electrode structures including capacitor structures having aluminum oxide diffusion barriers and methods of forming the same

ABSTRACT

A multilayer electrode structure has a conductive layer including aluminum, an oxide layer formed on the conductive layer, and an oxygen diffusion barrier layer. The oxide layer includes zirconium oxide and/or titanium oxide. The oxygen diffusion barrier layer is formed at an interface between the conductive layer and the oxide layer by re-oxidizing the oxide layer. The oxygen diffusion barrier layer includes aluminum oxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC §119 of Korean PatentApplication No. 10-2006-0039972, filed on May 3, 2006, the disclosure ofwhich is hereby incorporated herein by reference in its entirety as ifset forth fully herein.

FIELD OF THE INVENTION

The present invention relates to multilayer electrode structures,methods of forming multilayer electrode structures, capacitors includingmultilayer structures, and methods of forming capacitors.

BACKGROUND OF THE INVENTION

Integrated circuit devices are widely used in many consumers, commercialand other applications. In order to increase the integration density ofthe integrated circuit devices, it may be desirable to form smaller andsmaller devices.

Generally, memory devices such as dynamic random access memory (DRAM)and logic devices include capacitors. As is well known to those havingskill in the art, a capacitor includes two closely spaced apartelectrodes with a dielectric therebetween. A lower or bottom electrodemay be referred to as a “storage electrode”, and an upper or topelectrode may be referred to as a “plate electrode”. It is generallydesirable for a capacitor to have a fixed density and stable propertiesrelative to an applied voltage. A capacitor having a polysiliconinsulator polysilicon (PIP) structure has been widely employed in memorydevices or logic devices. Since polysilicon is stable at a hightemperature and a chemical vapor deposition (CVD) process may be used,the capacitor of the PIP structure may be easily manufactured.

However, a capacitance of the capacitor having the PIP structure mayvary in accordance with an applied voltage. Particularly, depletionlayers may be formed between the lower electrode and an insulation layerand between the insulation layer and the upper electrode when a voltageis applied to the capacitor having the PIP structure, because the lowerand the upper electrodes include doped polysilicon. As the depletionlayers are formed, a thickness of the insulation layer may increase sothat the capacitor may not have a stable capacitance. Further, thecapacitance of the capacitor having the PIP structure may be reducedfurther when the capacitor is employed in a highly integratedsemiconductor device having a design rule below about 90 nm.

A capacitor having a metal-insulator-metal (MIM) structure has also beendeveloped. The capacitor of the MIM structure includes electrodescomposed of metal. For example, Korean Laid-Open Patent Publication No.2003-2905 discloses a method of forming a capacitor having a MIMstructure. In the method of forming the capacitor, a dielectric layerincluding tantalum oxide is formed on a lower electrode of titaniumaluminum nitride. A heat treatment process is performed on thedielectric layer at a temperature of about 300° C. to about 500° C.using an oxygen plasma or UV/O₃ so as to re-oxidize the dielectriclayer. Then, a rapid thermal process or a furnace annealing process isexecuted on the dielectric layer. When the dielectric layer isre-oxidized and thermally treated, an aluminum oxide layer is formedbetween the lower electrode and the dielectric layer. The aluminum oxidelayer may prevent an oxidation of the lower electrode.

However, a thickness of the aluminum oxide layer formed at the interfacebetween the lower electrode and the dielectric layer may be large duringre-oxidizing and thermally treating the dielectric layer at a hightemperature. The aluminum oxide layer has a low dielectric constant suchthat dielectric characteristics of the dielectric layer may bedeteriorated when the aluminum oxide layer is thick. As a result, thecapacitor including the aluminum oxide layer may have a lowercapacitance.

SUMMARY OF THE INVENTION

Example embodiments of the present invention can provide multilayerstructures including a dielectric layer that can have a high dielectricconstant and a methods of forming the multilayer structure.

Example embodiments of the present invention can provide capacitorsincluding the multilayer structures and methods of forming thecapacitors.

According to some embodiments of the invention, there are providedmultilayer electrode structures that include a conductive layerincluding aluminum, an oxide layer on the conductive layer, and anoxygen diffusion barrier layer between the conductive layer and theoxide layer. As used herein, an “oxygen diffusion barrier layer” means alayer that reduces or even prevents diffusion of oxygen thereacross. Theoxide layer includes zirconium oxide and/or titanium oxide, and theoxygen diffusion barrier layer includes aluminum oxide. The oxygendiffusion barrier layer may be formed by re-oxidizing the oxide layer.In some embodiments, the oxygen diffusion barrier is directly on theconductive layer, and the oxide layer is directly on the oxygendiffusion barrier. In other embodiments, a plate electrode is providedon the oxide layer to provide a capacitor.

In example embodiments of the present invention, the oxygen diffusionbarrier layer may have thickness between about 2 Å and about 5 Å. Forexample, a thickness ratio between the oxide layer and the oxygendiffusion barrier layer may be in a range of about 15:1 to about 25:1.

In example embodiments of the present invention, the conductive layermay include titanium aluminum nitride and/or tantalum aluminum nitride.

According to another aspect of the present invention, there are providedmethods of forming a multilayer electrode structure. In these methods offorming the multilayer electrode structure, after forming a conductivelayer including aluminum, an oxide layer including zirconium oxideand/or titanium oxide is formed on the conductive layer. An oxygendiffusion barrier layer including aluminum oxide is formed at aninterface between the conductive layer and the oxide layer byre-oxidizing the oxide layer.

In example embodiments of the present invention, the conductive layermay be formed using a titanium precursor including titanium chloride(TiCl₄), at least one nitrogen precursor including ammonia (NH₃) and analuminum precursor including trimethyl aluminum (TMA).

In example embodiments of the present invention, the oxide layer may beformed using a zirconium precursor and an oxidizing agent and/or using atitanium precursor and an oxidizing agent.

In example embodiments of the present invention, re-oxidizing the oxidelayer may be performed using an oxygen plasma.

In example embodiments of the present invention, the oxide layer may becrystallized during re-oxidizing the oxide layer.

According to still other embodiments of the present invention, there areprovided capacitors that include a storage electrode including aluminum,a dielectric layer on the storage electrode, an oxygen diffusion barrierlayer at an interface between the storage electrode and the dielectriclayer, and a plate electrode on the dielectric layer. The dielectriclayer includes zirconium oxide and/or titanium oxide. The oxygendiffusion barrier layer includes aluminum oxide. The oxygen diffusionbarrier layer is formed by re-oxidizing the dielectric layer.

In example embodiments of the present invention, the storage electrodemay include titanium aluminum nitride and/or tantalum aluminum nitride.

In example embodiments of the present invention, a thickness ratiobetween the oxygen diffusion barrier layer and the dielectric layer maybe in a range of about 1:15 to about 1:25.

In example embodiments of the present invention, the plate electrode mayinclude radium or titanium nitride.

According to still other embodiments of the present invention, there areprovided methods of forming a capacitor. In these methods of forming thecapacitor, a storage electrode including aluminum is provided, and thena dielectric layer including zirconium oxide and/or titanium oxide isformed on the storage electrode. After an oxygen diffusion barrier layerincluding aluminum oxide is formed at an interface between the storageelectrode and the dielectric layer by re-oxidizing the dielectric layer,a plate electrode is formed on the dielectric layer.

In example embodiments of the present invention, re-oxidizing thedielectric layer may be performed using an oxygen plasma.

In example embodiments of the present invention, the oxygen diffusionbarrier layer may be formed at between about 200° C. and about 400° C.for about 2 to about 5 minutes.

In example embodiments of the present invention, the storage electrodemay be formed using a titanium precursor including titanium chloride, atleast one nitrogen precursor including ammonia and an aluminum precursorincluding trimethyl aluminum.

In example embodiments of the present invention, the oxide layer may beformed using a zirconium precursor and an oxidizing agent or using atitanium precursor and an oxidizing agent. Examples of the zirconiumprecursor may include tetra-tertiary-butoxy zirconium (Zr(OtBu)₄),tetrakis-ethyl-methyl-amino zirconium (Zr[N(CH₃)(C₂H₅)₄]), zirconiumiso-propoxide (Zr(OC₃H₇)₄), and/or tetra-methyl-hepta-diene zirconium(Zr(C₁₁H₁₉O₂)₄). Examples of the oxidizing agent may include an ozone(O₃) gas, an oxygen (O₂) gas, water vapor (H₂O), an oxygen (O₂) plasmaand/or a remote oxygen (O₂) plasma. Examples of the titanium precursormay include tetra-tertiary-butoxy titanium (Ti(OtBu)₄),tetrakis-ethyl-methyl-amino titanium (Ti[N(CH₃)(C₂H₅)₄]), titaniumethoxide (Ti(OEt)₄), titanium iso-propoxide (Ti(OC₃H₇)₄),tetra-methyl-hepta-diene titanium (Ti(C₁₁H₁₉O₂)₂) and/ortetra-methyl-hepta-diene zirconium (Zr(C₁₁H₁₉O₂)₄).

According to example embodiments of the present invention, an oxygendiffusion barrier layer having thickness between about 2 Å and about 5 Åmay be formed between the storage electrode and the dielectric layer sothat an oxidation of the storage electrode may be effectively reduced orprevented in a re-oxidation of the dielectric layer so as to allow adesired capacitance.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detailed example embodimentsthereof with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view illustrating a multilayer structure inaccordance with example embodiments of the present embodiment;

FIGS. 2 to 4 are cross-sectional views illustrating methods of forming amultilayer structure in accordance with example embodiments of thepresent invention;

FIG. 5 is a cross-sectional view illustrating a capacitor in accordancewith example embodiments of the present invention; and

FIGS. 6 to 10 are cross-sectional views illustrating methods of forminga capacitor in accordance with example embodiments of the presentinvention.

DESCRIPTION OF THE EMBODIMENTS

The present invention is described more fully hereinafter with referenceto the accompanying drawings, in which example embodiments of thepresent invention are shown. The present invention may, however, beembodied in many different forms and should not be construed as limitedto the example embodiments set forth herein. Rather, these exampleembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. In the drawings, the sizes and relative sizesof layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like reference numerals refer tolike elements throughout. As used herein, the term “and/or” includes anyand all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentinvention. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Example embodiments of the present invention are described herein withreference to cross-section illustrations that are schematicillustrations of idealized embodiments (and intermediate structures) ofthe present invention. As such, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, example embodiments of thepresent invention should not be construed as limited to the particularshapes of regions illustrated herein but are to include deviations inshapes that result, for example, from manufacturing. For example, animplanted region illustrated as a rectangle will, typically, haverounded or curved features and/or a gradient of implant concentration atits edges rather than a binary change from implanted to non-implantedregion. Likewise, a buried region formed by implantation may result insome implantation in the region between the buried region and thesurface through which the implantation takes place. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the actual shape of a region of a device andare not intended to limit the scope of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, multilayer electrode structures according to exampleembodiments of the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 1 is a cross-sectional view illustrating a multilayer electrodestructure in accordance with example embodiments of the presentembodiment.

Referring to FIG. 1, a conductive layer 102 including aluminum (Al) isprovided on a substrate, such as a semiconductor substrate 100. Inexample embodiments, the conductive layer 102 may include a metal filmincluding aluminum so that characteristics of the conductive layer 102may be not changed in a re-oxidation process performed at between about200° C. and about 400° C. For example, the conductive layer 102 mayinclude a titanium aluminum nitride (TiAlN) film or a tantalum aluminumnitride (TaAlN) film.

An oxide layer 104 having a high dielectric constant is formed on theconductive layer 102. The oxide layer 104 may include zirconium oxideand/or titanium oxide.

An oxygen diffusion barrier layer 106 is formed at an interface betweenthe conductive layer 102 and the oxide layer 104. The oxygen diffusionbarrier layer 106 may be formed in a re-oxidation process.

In example embodiments of the present invention, the oxygen diffusionbarrier layer 106 may include aluminum oxide. The oxygen diffusionbarrier layer 106 may range in thickness from about 2 Å to about 5 Å.The thickness of the oxygen diffusion barrier layer 106 may besubstantially the same as a thickness of an aluminum oxide film formedby performing one cycle of an atomic layer deposition (ADL) process. Inother words, the oxygen diffusion barrier layer 106 may have a thicknesssubstantially the same as that of a mono-layer. A thickness ratiobetween the oxide layer 104 and the oxygen diffusion barrier layer 106may be in a range of about 15:1 to about 25:1.

When the oxygen diffusion barrier layer 106 has a thickness considerablythinner than that of the oxide layer 104, the oxygen diffusion barrierlayer 106 may not have an affect on dielectric properties of the oxidelayer 104, but may reduce or effectively prevent oxygen from diffusinginto the conductive layer 102.

Hereinafter, methods of forming a multilayer structure according toexample embodiments of the present invention will be described in detailwith reference to the accompanying drawings.

FIGS. 2 to 4 are cross-sectional views illustrating methods of forming amultilayer structure in accordance with example embodiments of thepresent invention.

Referring to FIG. 2, a conductive layer 102 including aluminum is formedon a substrate such as a semiconductor substrate 100. The semiconductorsubstrate 100 may include a plurality of conductive patterns formedthereon. The conductive layer 102 may include titanium aluminum nitrideand/or tantalum aluminum nitride.

In example embodiments of the present invention, the semiconductorsubstrate 100 or the semiconductor substrate 100 having the conductivepatterns may be loaded in a process chamber. A titanium precursor suchas titanium chloride (TiCl₄) may be introduced into the process chamber.The titanium precursor may be chemically and physically absorbed to thesemiconductor substrate 100 or the semiconductor substrate 100 havingthe conductive patterns.

A first purge gas may be introduced into the process chamber to removeremaining titanium precursor in the process chamber and physisorbed(i.e., physically absorbed) titanium precursor to the semiconductorsubstrate 100. The first purge gas may include an inactive gas such asan argon (Ar) gas, a helium (He) gas, a nitrogen (N₂) gas, etc.

A first nitrogen precursor such as ammonia (NH₃) may be introduced intothe process chamber. The first nitrogen precursor may be chemically andphysically absorbed to the titanium precursor chemisorbed (i.e.,chemically absorbed) to the semiconductor substrate 100.

A second purge gas may be introduced into the process chamber to removeremaining first nitrogen precursor in the process chamber andphysisorbed first nitrogen precursor. Accordingly, a titanium nitridefilm may be formed on the semiconductor substrate 100 or thesemiconductor substrate 100 having the conductive patterns. The secondpurge gas may include an inactive gas such as an argon gas, a heliumgas, a nitrogen gas, etc.

An aluminum precursor such as trimethyl aluminum (TMA) may be introducedinto the process chamber. The aluminum precursor may be chemically andphysically absorbed to the titanium nitride film.

A third purge gas may be introduced into the process chamber to removeremaining aluminum precursor in the process chamber and physisorbedaluminum precursor. The third purge gas may include an inactive gas suchas an argon gas, a helium gas, a nitrogen gas, etc.

A second nitrogen precursor may be introduced into the process chamber.The second nitrogen precursor may include a material substantially thesame as that of the first nitrogen precursor. For example, the secondnitrogen precursor may include ammonia (NH₃). The second nitrogenprecursor may be chemically and physically absorbed to the aluminumprecursor chemisorbed to the titanium nitride film.

A fourth purge gas may be introduced into the process chamber to removethe second nitrogen precursor remaining in the process chamber andphysisorbed second nitrogen precursor. Therefore, a titanium aluminumnitride film may be formed on the semiconductor substrate 100 or thesemiconductor substrate 100 having the conductive patterns. The fourthpurge gas may include an inactive gas such as an argon gas, a heliumgas, a nitrogen gas, etc.

As described above, the titanium precursor, the first nitrogenprecursor, the aluminum precursor and the second nitrogen precursor maybe successively provided onto the semiconductor substrate 100 in theprocess chamber, such that the titanium aluminum nitride film having athickness of about several Ångstroms may be formed on the semiconductorsubstrate 100. When the above-described cycle may be repeatedly carriedout, a titanium aluminum nitride layer having a desired thickness may beformed on the semiconductor substrate 100. The titanium nitride layer ofthe desired thickness may correspond to the conductive layer 102.

Aluminum included in the titanium aluminum nitride layer may reduce orprevent the titanium aluminum nitride layer from being oxidized in asuccessive re-oxidation process because aluminum may serve as ananti-oxidizing agent in the re-oxidation process. This mechanism will bedescribed later.

Referring to FIG. 3, an oxide layer 104 including zirconium oxide and/ortitanium oxide is formed on the conductive layer 102.

In one example embodiment of the present invention, the semiconductorsubstrate 100 having the conductive layer 102 formed thereon may beloaded in a process chamber. A zirconium precursor may be provided intothe process chamber. Examples of the zirconium precursor may includetetra-tertiary-butoxy zirconium (Zr(OtBu)₄), tetrakis-ethyl-methyl-aminozirconium (Zr[N (CH₃)(C₂H₅)₄]), zirconium iso-propoxide (Zr(OC₃H₇)₄),tetra-methyl-hepta-diene zirconium (Zr(C₁₁H₁₉O₂)₄), etc. The zirconiumprecursor may chemically and physically absorbed to a surface of theconductive layer 102. Then, a first purge process may be performed toremove physisorbed zirconium precursor and remaining zirconium precursorin the process chamber. An oxidizing agent may be introduced into theprocess chamber. The oxidizing agent may oxidize chemisorbed zirconiumprecursor. Examples of the oxidizing agent may include an ozone (O₃)gas, an oxygen (O₂) gas, water vapor (H₂O), an oxygen (O₂) plasma, aremote oxygen (O₂) plasma, etc. Thus, a zirconium oxide film may beformed on the conductive layer 102. When the zirconium precursor and theoxidizing agent are repeatedly introduced into the process chamber, azirconium oxide layer having a desired thickness may be formed on theconductive layer 102. The zirconium oxide layer may correspond to theoxide layer 104.

In another example embodiment of the present invention, thesemiconductor substrate 100 having the conductive layer 102 thereon maybe loaded in a process chamber. A titanium precursor may be introducedinto the process chamber.

Examples of the titanium precursor may include tetra-tertiary-butoxytitanium (Ti(OtBu)₄), tetrakis ethyl methyl amino titanium(Ti[N(CH₃)(C₂H₅)₄]), titanium ethoxide (Ti(OEt)₄), titaniumiso-propoxide (Ti(OC₃H₇)₄), tetra-methyl-hepta-diene titanium(Ti(C₁₁H₁₉O₂)₂), etc. The titanium precursor may be chemisorbed andphysisorbed to a surface of the conductive layer 102. The physisorbedtitanium precursor and remaining titanium precursor may be removed fromthe process chamber by a purge process. An oxidizing agent may beintroduced into the process chamber. Examples of the oxidizing agent mayinclude an ozone (O₃) gas, an oxygen (O₂) gas, water vapor (H₂O), anoxygen (O₂) plasma, a remote oxygen (O₂) plasma, etc. A titanium oxidelayer film may be formed on the conductive layer 102.

When the titanium precursor and the oxidizing agent are repeatedlyintroduced into the process chamber, a titanium oxide layer having adesired thickness may be formed on the conductive layer. The titaniumoxide layer may correspond to the oxide layer 104. The oxide layer 104formed by the above-described process may have a high dielectricconstant so that the oxide layer 104 formed on the conductive layer 102may advantageously serve as a dielectric layer.

Referring to FIG. 4, an oxygen diffusion barrier layer 106 is formed atan interface between the conductive layer 102 and the oxide layer 104 byre-oxidizing the oxide layer 104.

In example embodiments of the present invention, a re-oxidation processmay be performed on the semiconductor substrate 100 having theconductive layer 102 and the oxide layer 104. The re-oxidation processmay be carried out using an oxygen plasma at between about 500 Pa andabout 1,000 Pa pressure and between about 200° C. and about 400° C.temperature for about 2 minutes to about 5 minutes.

In the re-oxidation process, a sufficient amount of oxygen may beprovided into the oxide layer 104 so that the oxide layer 104 maysufficiently include oxygen.

In addition, zirconium oxide or titanium oxide in the oxide layer 104may be crystallized between about 200° C. and about 400° C. such thatthe oxide layer 104 may be sufficiently crystallized in the re-oxidationprocess. Therefore, an additional heat treatment process forre-oxidizing the oxide layer 104 may be omitted.

While the re-oxidation process is executed at between about 200° C. andabout 400° C., an aluminum oxide layer may be formed at the interfacebetween the conductive layer 102 and the oxide layer 104. For example,aluminum in the conductive layer 102 may be oxidized in the re-oxidationprocess such that the aluminum oxide layer serving as the oxygendiffusion preventing layer 106 may be formed between the conductivelayer 102 and the oxide layer 104.

The oxygen diffusion barrier layer 106 may have thickness of betweenabout 2 Å and about 5 Å, which may be obtained by performing one cycleof an ALD process. That is, a thickness of the oxygen diffusion barrierlayer 106 may be substantially the same as that of a mono-layer.

As the thickness of the oxygen diffusion barrier layer 106 includingaluminum oxide increases, the oxygen diffusion barrier layer 106 mayhave a high dielectric constant although aluminum oxide has a relativelylow dielectric constant. Thus, the oxygen diffusion barrier layer 106may have a thickness considerably thinner than that of the oxide layer104 so as to maintain dielectric characteristics of the oxide layer 104.As a result, the oxide layer 104 may advantageously serve as thedielectric layer because of the very thin oxygen diffusion barrier layer106.

Hereinafter, capacitors according to example embodiments of the presentinvention will be described in detail with reference to the accompanyingdrawings.

FIG. 5 is a cross-sectional view illustrating a capacitor in accordancewith example embodiments of the present invention.

Referring to FIG. 5, a storage electrode 230 including aluminum isprovided on a substrate such as a semiconductor substrate 200. Anisolation layer 202 may be formed on the semiconductor substrate 200. Aplurality of conductive patterns may be formed on the semiconductorsubstrate 200. For example, gate structures, impurity regions, pads andinsulation structures may be provided between the semiconductorsubstrate 200 and the storage electrode 230. Each of the gate structuresmay include a gate oxide layer pattern 204, a gate conductive layerpattern 206 and a mask pattern 208 formed on the semiconductor substrate200. A spacer 210 may be provided on a sidewall of each gate structure.Impurity regions 212 may be formed portions of the semiconductorsubstrate 200 adjacent to the gate structures. Pads 215 may beelectrically connected to the impurity regions 212. A plurality ofinsulating interlayers may be provided on the semiconductor substrate200 to cover the gate structure and the pads 215. Storage node contacts220 may be formed through the insulating interlayers and titaniumsilicide layers 226 may be provided on the storage node contacts 220.The fabrication processes described in this paragraph can beconventional and need not be described further herein.

The storage electrode 230 may have a cylindrical shape electricallyconnected to the conductive patterns such as the storage node contact226 and/or the pad pattern 226. The storage electrode 230 may correspondto a metal nitride layer including aluminum. Electric characteristics ofthe storage electrode 230 may not be changed in a successivere-oxidation process performed at between about 200° C. and about 400°C. For example, the storage electrode 230 may include titanium aluminumnitride and/or tantalum aluminum nitride.

A dielectric layer 232 including zirconium oxide and/or titanium oxideis formed on the storage electrode 230. The dielectric layer 232 may beuniformly formed on the storage electrode 230 so that an inside of thestorage electrode 230 may not be completely filled with the dielectriclayer 232.

The dielectric layer 232 including zirconium oxide and/or titanium oxidemay have a desired thickness that ensures a sufficiently high dielectricconstant and a low leakage current. When the dielectric layer 232includes zirconium oxide, a thickness of the dielectric layer 232 may beabout 100 Å.

An oxygen diffusion barrier layer 234 is formed at an interface betweenthe storage electrode 230 and the dielectric layer 232. The oxygendiffusion barrier layer 234 may include aluminum oxide. The oxygendiffusion barrier layer 234 may be formed by the re-oxidation processfor the dielectric layer 232.

The oxygen diffusion barrier layer 234 may be in a range of about 2 Å toabout 5 Å in thickness. The thickness of the oxygen diffusion barrierlayer 234 may be substantially the same as that of a mono-layer obtainedby one cycle of an ALD process. When a thickness of the dielectric layer232 is about 100 Å, a thickness ratio between the oxygen diffusionbarrier layer 234 and the dielectric layer 232 may be in a range ofabout 1:15 to about 1:25.

The oxygen diffusion barrier layer 234 may have a relatively lowdielectric constant and may reduce or prevent oxygen from diffusing intothe storage electrode 230. Thus, the oxygen diffusion barrier layer 234may be formed on the storage electrode 230 to be thin, therebymaintaining a high dielectric constant of the capacitor having thedielectric layer 232.

A plate electrode 236 is formed on the dielectric layer 232. The plateelectrode 236 may include a metal such as radium or a metal nitride suchas titanium nitride.

As described above, the capacitor including the storage electrode 230,the oxygen diffusion barrier layer 234, the dielectric layer 232 and theplate electrode 236 may be provided on the semiconductor substrate 200.The oxygen diffusion barrier layer 234 may reduce or prevent anoxidation of the storage electrode 230 which can improve electricalcharacteristics of the capacitor. Additionally, the capacitor may have adesired high capacitance because of the dielectric layer 232 having thehigh dielectric constant.

Hereinafter, methods of forming a capacitor according to exampleembodiments of the present invention will be described in detail withreference to the accompanying drawings.

FIGS. 6 to 10 are cross-sectional views illustrating methods of forminga capacitor in accordance with example embodiments of the presentinvention.

Referring to FIG. 6, a substrate such as a semiconductor substrate 200is divided into an active region and a field region by an isolationprocess. The field region may be formed in accordance with a formationof a trench isolation layer 202 so as to improve an integration degreeof the capacitor.

A thin gate oxide layer pattern 204 is formed on the semiconductorsubstrate 200 including the isolation layer 202. The gate oxide layermay be formed by a thermal oxidation process or a chemical vapordeposition (CVD) process. Gate conductive layer patterns 206 and gatemask patterns 208 are formed on the gate oxide layer patterns 204,respectively. Thus, gate structures may be formed on the semiconductorsubstrate 200. Each of the gate structure includes the gate oxide layerpattern 204, the gate conductive layer pattern 206 and the gate maskpattern 208. The gate structures may be disposed as line shapes on thesemiconductor substrate 200.

A silicon nitride layer is formed on the semiconductor substrate 200 tocover the gate structures, and then the silicon nitride layer isselectively removed by an anisotropic etching process. Hence, a gatespacer 210 is formed on a sidewall of each gate structure.

Impurities are implanted into portions of the semiconductor substrate200 exposed between the gate structures using the gate structures as ionimplantation masks. Then, source/drain regions 212 are formed on thesemiconductor substrate 200 after a thermal treatment process isperformed on the implanted impurities.

As a result, transistors having the gate structures and the source/drainregions 212 are formed on the semiconductor substrate 200. Theline-shaped gate structures may serve as word lines. The source/drainregions 212 may be defined in accordance with an operation mode of eachtransistor. A bit line may be electrically connected to a source regionwhereas a capacitor may be electrically connected to a drain region.

A first insulating interlayer 214 is formed on the semiconductorsubstrate 200 to cover the transistors. The first insulating interlayer214 may be formed using an oxide such as silicon oxide. The firstinsulating interlayer 214 is partially etched to form first contactholes (not shown) exposing the source/drain regions 216.

Pads 215 are formed in the first contact holes by filling the firstcontact holes with conductive materials.

A second insulating interlayer 216 is formed on the first insulatinginterlayer 214. The second insulating interlayer 216 may also be formedusing an oxide such as silicon oxide. The second insulating interlayer216 is partially etched to form a second contact hole (not shown) thatexposes one of the pads 215 making contact with the source region. Aconductive layer is formed in the second contact hole and on the secondinsulating interlayer 216, and then a bit line (not shown) and a bitline contact (not shown) are formed by patterning the conductive layer.The bit line contact may be positioned in the second contact hole andthe bit line may be formed on the bit line contact.

A third insulating interlayer 218 is formed on the second insulatinginterlayer 216 to cover the bit line. The third insulating interlayer218 may be formed using oxide. The third insulating interlayer 218 andthe second insulating interlayer 216 are partially etched to form thirdcontact holes (not shown) exposing the pads 215 electrically connectedto the drain regions.

Storage node contacts 220 are formed in the third contact holes byfilling the third contact holes with conductive materials, respectively.For example, the storage node contacts 220 may be formed usingpolysilicon.

In an example embodiment of the present invention, pad patterns (notshown) may be formed on the storage node contacts 220 so as to defineportions where storage electrodes 230 (see FIG. 8) are positioned.

An etch-stop layer 222 is formed on the storage node contact 220 and thethird insulating interlayer 218. The etch-stop layer 222 may be formedusing a nitride such as silicon nitride.

Referring to FIG. 7, a mold layer 224 is formed on the etch-stop layer222. The mold layer 224 may be formed using an insulation material suchas silicon oxide.

The mold layer 224 may serve as a mold for forming the storage electrode230 having a cylindrical shape. The mold layer 224 may be formed usingan oxide such as silicon oxide. A height of the storage electrode 230having the cylindrical shape may mainly depend on a thickness of themold layer 224. Thus, the thickness of the mold layer 224 may becontrolled in accordance with a desired capacitance of the capacitor.

A hard mask pattern (not shown) is formed on the mold layer 224. Thehard mask pattern may expose a portion of the mold layer 224 where thestorage electrode 230 having the cylindrical shape is positioned. Thatis, the exposed portion of the mold layer 224 may correspond to anopening 225 for the storage electrode 230. The hard mask pattern may beformed using a material having a high selectivity relative to the moldlayer 224. For example, the hard mask pattern may be formed usingpolysilicon.

The mold layer 224 and the etch-stop layer 222 are partially etchedusing the hard mask pattern as an etching mask so that the openingportion 225 exposing the storage node contact 220 is formed through themold layer 224 and the etch-stop layer 222.

A titanium silicide layer 226 is formed on the storage node contact 220exposed by the opening 225. The titanium silicide layer 226 may beeasily formed on a layer of silicon whereas the titanium silicide layer226 may be hardly formed on a layer of silicon oxide or silicon nitride.Accordingly, the titanium silicide layer 226 may be selectively formedon the storage node contact 220 except for the third insulatinginterlayer 218, the etch-stop layer 222 and the mold layer 224.

Referring to FIG. 8, a conductive layer (not shown) for forming thestorage electrode 230 is formed on a sidewall of the opening 225, thetitanium silicide layer 226 and the mold layer 224. The conductive layermay include aluminum so that the storage electrode 230 may not beoxidized in the successive re-oxidation process. For example, theconductive layer may be formed using titanium aluminum nitride and/ortantalum aluminum nitride because titanium aluminum nitride and tantalumaluminum nitride have the high anti-oxidation characteristics. Inexample embodiments, the conductive layer for the storage electrode 230may be formed by a process substantially the same as the processdescribed with reference to FIG. 2.

A sacrificial layer 228 is formed on the conductive layer for thestorage electrode 230 to sufficiently fill up the opening 215. Thesacrificial layer 228 may be formed using an oxide such as siliconoxide. For example, the sacrificial layer 228 may be formed usingBoroPhosphoSilicate Glass (BPSG) or undoped silicate glass (USG).

The conductive layer and the hard mask pattern are removed until themold layer 224 is exposed to form the storage electrode 230. The storageelectrode 230 may be formed by a planarization process such as achemical mechanical polishing (CMP) process and/or an etch-back process.That is, portions of the conductive layer on the sidewall of the opening215 and the titanium silicide layer 226 may correspond to the storageelectrode 230.

Referring to FIG. 9, after forming the storage electrode 230, the moldlayer 224 is removed from the storage electrode 230. The mold layer 224may be removed by a wet etching process. While removing the mold layer224, the sacrificial layer 228 filling the opening 215 is simultaneouslyremoved from the storage electrode 230 so that an inside and an outsideof the storage electrode 230 are exposed.

A dielectric layer 232 is formed on the storage electrode 230. Thedielectric layer 232 may be formed using a metal oxide such as zirconiumoxide and/or titanium oxide. Thus, the dielectric layer 232 may have ahigh dielectric constant.

The dielectric layer 232 including the metal oxide may havecrystallization temperature substantially lower than that of adielectric layer including tantalum oxide. The dielectric layer 232 maybe crystallized in the re-oxidation process performed at between about200° C. and about 400° C. using an oxygen plasma. Therefore, anadditional heat treatment for crystallizing the dielectric layer 232 maybe omitted. The dielectric layer 232 including the metal oxide may beformed by a process substantially the same as that described withreference to FIG. 3.

Referring to FIG. 10, an oxygen diffusion barrier layer 234 includingaluminum oxide is formed at an interface between the storage electrode230 and the dielectric layer 232 by the re-oxidation process. That is,the dielectric layer 232 is re-oxidized to form the oxygen diffusionbarrier layer 234 between the storage electrode 230 and the dielectriclayer 232. The re-oxidation process may be performed using the oxygenplasma process substantially the same as that described with referenceto FIG. 4.

In the re-oxidation process, oxygen may be provided into the dielectriclayer 232 so that the dielectric layer 232 may have a sufficient amountof oxygen. Thus, the dielectric layer 232 may provide a high dielectricconstant. Further, aluminum in the storage electrode 230 may bepartially oxidized to form the oxygen diffusion barrier layer 234including aluminum oxide.

The oxygen diffusion barrier layer 234 may reduce and even preventoxygen in the dielectric layer 232 from diffusing into the storageelectrode 230 in the re-oxidation process performed using the oxygenplasma. The oxygen diffusion barrier layer 234 may have thicknessbetween about 2 Å and about 5 Å, which may be substantially the same asthat of a mono-layer of aluminum oxide obtained by one cycle of an ALDprocess.

Since the dielectric layer 232 has the thickness of about 10 Å and theoxygen diffusion barrier layer 234 has thickness between about 2 Å andabout 5 Å, a thickness ratio between the dielectric layer 232 and theoxygen diffusion barrier layer 234 may be in a range of about 15:1 toabout 25:1.

When the oxygen diffusion barrier layer 234 is relatively thick,dielectric characteristics of the dielectric layer 232 may be reducedbecause the oxygen diffusion barrier layer 234 has a relatively lowdielectric constant. Therefore, the dielectric layer 232 may have apredetermined thickness to allow the high dielectric constant whereasthe oxygen diffusion barrier layer 234 may have a thickness considerablythinner than that of the dielectric layer 232 without deteriorating thedielectric characteristics of the dielectric layer 232.

When the re-oxidation process is carried out at between about 200° C.and about 400° C., the metal oxide included in the dielectric layer 232may be crystallized. Thus, manufacturing processes for the capacitor maybe simplified by omitting an additional crystallization process for thedielectric layer 232.

As shown in FIG. 5, a plate electrode 236 is formed on the dielectriclayer 232. The plate electrode 236 may be formed a metal such as radiumand/or a metal nitride such as titanium nitride. As a result, thecapacitor including the storage electrode 230, the oxygen diffusionbarrier layer 234, the dielectric layer 232 and the plate electrode 236is formed over the semiconductor substrate 200.

Since the oxygen diffusion barrier layer 234 and the dielectric layer232 are formed on the storage electrode 230, the diffusion of oxygeninto the storage electrode 230 may be reduced or effectively preventedin the re-oxidation process. Additionally, the oxygen diffusion barrierlayer 234 may be much thinner than that of the dielectric layer 232 suchthat the dielectric layer 232 may sufficiently provide the highdielectric constant for the desired capacitance of the capacitor.

According to example embodiments of the present invention, an oxygendiffusion barrier layer that is quite thin may be formed between astorage electrode including aluminum and a dielectric layer includingmetal oxide. Hence, an oxidation of the storage electrode may be reducedor efficiently prevented. Further, the dielectric layer having a highdielectric constant may be formed on the oxygen diffusion barrier layerso that a capacitor including the dielectric layer may have a desiredcapacitance.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few example embodiments of thepresent invention have been described, those skilled in the art willreadily appreciate that many modifications are possible in the exampleembodiments without materially departing from the novel teachings andadvantages of the present invention. Accordingly, all such modificationsare intended to be included within the scope of the present invention asdefined in the claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents but also equivalentstructures. Therefore, it is to be understood that the foregoing isillustrative of the present invention and is not to be construed aslimited to the specific embodiments disclosed, and that modifications tothe disclosed embodiments, as well as other embodiments, are intended tobe included within the scope of the appended claims. The presentinvention is defined by the following claims, with equivalents of theclaims to be included therein.

1. A multilayer electrode structure comprising: a conductive layerincluding aluminum; an oxide layer on the conductive layer, the oxidelayer including zirconium oxide and/or titanium oxide; and an oxygendiffusion barrier layer between the conductive layer and the oxidelayer, the oxygen diffusion barrier layer including aluminum oxide. 2.The multilayer electrode structure of claim 1, wherein the oxygendiffusion barrier layer has thickness between about 2 Å and about 5 Å.3. The multilayer electrode structure of claim 1, wherein the conductivelayer includes titanium aluminum nitride and/or tantalum aluminumnitride.
 4. The multilayer electrode structure of claim 1, wherein athickness ratio between the oxide layer and the oxygen diffusion barrierlayer is in a range of about 15:1 to about 25:1.
 5. The multilayerelectrode structure of claim 1 wherein the oxygen diffusion barrierlayer is directly on the conductive layer, and the oxide layer isdirectly on the oxygen diffusion barrier layer.
 6. The multilayerelectrode structure of claim 1 wherein the oxygen diffusion barrierlayer is formed by re-oxidizing the oxide layer.
 7. The multilayerelectrode structure of claim 1 further comprising: a plate electrode onthe dielectric layer, to provide a capacitor.
 8. The multilayerelectrode structure of claim 7, wherein the plate electrode includesradium or titanium nitride.
 9. A method of forming a multilayerelectrode structure, comprising: forming a conductive layer includingaluminum; forming an oxide layer on the conductive layer, the oxidelayer including zirconium oxide or titanium oxide; and re-oxidizing theoxide layer to form an oxygen diffusion barrier layer including aluminumoxide at an interface between the conductive layer and the oxide layer.10. The method of claim 9, wherein the conductive layer is formed usinga titanium precursor including titanium chloride (TiCl₄), at least onenitrogen precursor including ammonia (NH₃) and an aluminum precursorincluding trimethyl aluminum (TMA).
 11. The method of claim 9, whereinthe oxide layer is formed using a zirconium precursor and an oxidizingagent and/or using a titanium precursor and an oxidizing agent.
 12. Themethod of claim 9, wherein re-oxidizing the oxide layer is performedusing an oxygen plasma.
 13. The method of claim 9, wherein the oxidelayer is crystallized during re-oxidizing the oxide layer.
 14. Themethod of claim 9 further comprising: forming a plate electrode on thedielectric layer, to provide a capacitor.
 15. The method of claim 14,wherein re-oxidizing the dielectric layer is performed using an oxygenplasma.
 16. The method of claim 15, wherein the oxygen diffusion barrierlayer is formed at between about 200° C. and about 400° C. for about 2to about 5 minutes.
 17. The method of claim 14, wherein the storageelectrode is formed using a titanium precursor including titaniumchloride, at least one nitrogen precursor including ammonia and analuminum precursor including trimethyl aluminum.
 18. The method of claim14, wherein the oxide layer is formed using a zirconium precursor and anoxidizing agent and/or using a titanium precursor and an oxidizingagent.
 19. The method of claim 18, wherein the zirconium precursorincludes at least one selected from the group consisting oftetra-tertiary-butoxy zirconium (Zr(OtBu)₄), tetrakis-ethyl-methyl-aminozirconium (Zr[N(CH₃)(C₂H₅)₄]), zirconium iso-propoxide (Zr(OC₃H₇)₄), andtetra-methyl-hepta-diene zirconium (Zr(C₁₁H₁₉O₂)₄), and the oxidizingagent includes at least one selected from the group consisting of anozone (O₃) gas, an oxygen (O₂) gas, water vapor (H₂O), an oxygen (O₂)plasma and a remote oxygen (O₂) plasma.
 20. The method of claim 18,wherein the titanium precursor includes at least one selected from thegroup consisting of tetra-tertiary-butoxy titanium (Ti(OtBu)₄),tetrakis-ethyl-methyl-amino titanium (Ti[N(CH₃)(C₂H₅)₄]), titaniumethoxide (Ti(OEt)₄), titanium iso-propoxide (Ti(OC₃H₇)₄),tetra-methyl-hepta-diene titanium (Ti(C₁₁H₁₉O₂)₂) andtetra-methyl-hepta-diene zirconium (Zr(C₁₁H₁₉O₂)₄) and the oxidizingagent includes at least one selected from the group consisting of anozone (O₃) gas, an oxygen (O₂) gas, water vapor (H₂O), an oxygen (O₂)plasma and a remote oxygen (O₂) plasma.